Dermatologists and plastic surgeons have used various methods for removing superficial skin layers to cause the growth of new skin layers (i.e., commonly described as skin resurfacing techniques) since the early 1900's. Early skin resurfacing treatments used an acid such as phenol to etch away surface layers of a patient's skin that contained damage to thereafter be replaced by new skin. (The term damage when referring to a skin disorder is herein defined as any cutaneous defect, e.g., including but not limited to rhytides, hyperpigmentation, acne scars, solar elastosis, other dyschromias, stria distensae, seborrheic dermatitis).
Following the removal of surface skin layers at a particular depth, no matter the method of skin removal, the body's natural wound-healing response begins to regenerate the epidermis and underlying wounded skin layers. The new skin layer will then cytologically and architecturally resemble younger and more normal skin. The range of resurfacing treatments can be divided generally into three categories based on the depth of the skin removal and wound: (i) superficial exfoliations or peels extending into the epidermis, (ii) medium-depth resurfacing treatments extending into the papillary dermis, and (iii) deep resurfacing treatments that remove tissue to the depth of the reticular dermis.
Microdermabrasion uses an air-pressure source to deliver abrasive particles directly against a patient's skin at high-velocities to abrade away skin layers. Microdermabrasion as currently practiced falls into the category of a superficial resurfacing treatment.
It is useful to briefly explain the body's mechanism of actually resurfacing skin in response to the removal of a significant depth of dermal layers. Each of the above-listed depths of treatment disrupts the epidermal barrier, or a deeper dermal barrier (papillary or reticular), which initiates varied levels of the body's wound-healing response. A superficial skin layer removal typically causes a limited wound-healing response, including a transient inflammatory response and limited collagen synthesis within the dermis. In a medium-depth or a deep treatment, the initial inflammatory stage leads to hemostasis through an activated coagulation cascade. Chemotactic factors and fibrin lysis products cause neutrophils and monocytes to appear at the site of the wound. The neutrophils sterilize the wound site and the monocytes convert to macrophages and elaborate growth factors which initiate the next phase of the body's wound-healing response involving granular tissue formation. In this phase, fibroblasts generate a new extracellular matrix, particularly in the papillary and reticuilar dermis, which is sustained by angiogenesis and protected anteriorly by the reforming epithelial layer. The new extracellular matrix is largely composed of collagen fibers (particularly Types I and III) which are laid down in compact parallel arrays. It is largely the collagen fibers that provide the structural integrity of the new skin—and contribute to the appearance of youthful skin.
All of the prevalent types of skin damage (rhytides, solar elastosis effects, hyperpigmentation, acne scars, dyschromias, melasma, stria distensae) manifest common histologic and ultrastructural characteristics, which in particular include disorganized and thinner collagen aggregates, abnormalities in elastic fibers, and abnormal fibroblasts, melanocytes and keratinocytes that disrupt the normal architecture of the dermal layers. It is well recognized that there will be a clinical improvement in the condition and appearance of a patient's skin when a more normal architecture is regenerated by the body's wound-healing response. Of most significance to a clinical improvement in skin is the creation of more dense parallel collagen aggregates with decreased periodicity (spacing between fibrils). The body's wound-healing reaction is responsible for synthesis of these collagen aggregates.
The superficial treatment offered by microdermabrasion has the advantages of being performed without anesthetics and requiring no extended post-treatment recovery period. However, microdermabrasion as currently practiced also has a large disadvantage. Current microdermabrasion devices cause abrasive effects in a focused area of the skin that is very small, for example roughly 20 mm2 to 200 mm2, since all current devices use a single-hole orifice that jets air and abrasives to strike the skin in a highly focused area. Such a focused treatment area is suitable mainly for superficial exfoliations when the proximal end of the device is passed over the skin in overlapping paths.
An important part of creating the skin healing response is the mechanical stretching of the skin caused by the vacuum hand piece. However, different regions of skin have different thickness and elasticity. For example, the eyelids are roughly 0.3 mm thick, while the skin on the back is roughly 3.0 mm thick. Obviously, applying the same vacuum level to various regions of the skin may cause a range of effects, including no effect, acute trauma or somewhere in between. The vacuum level is set by the operator, and the amount of vacuum is established, based in great part, due to the experience of the operator. Even with an experienced operator, working on a specific region of the body, for example face and neck, the vacuum level must be continuously adjusted to maintain the balance between too little mechanical stretching (with no benefit) and too much mechanical stretching (causing trauma).